Coax Cable Loss Calculator
Estimate coax cable signal loss and attenuation over distance and frequency for antenna runs with this free calculator in your browser.
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Enter Values
Minimum 0
Enter your values and press Calculate to see results.
How to use this calculator
- Enter the cable's loss per 100 m and the run length.
- Read the total loss and power delivered.
How it works
Total loss (dB) = loss per 100 m × length ÷ 100; power delivered = 10^(−loss/10).
Worked example
13 dB/100 m, 20 m. 2.6 dB loss — ~55% of power reaches the end.
Common mistakes
- Loss rises with frequency — use the rated figure for your band.
- Ignoring connector losses, which add up.
Frequently asked questions
How much loss is too much?
Every 3 dB halves your power. Keep feedline loss low, especially at VHF/UHF and above.
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Cite this tool
Zerdly. (2026). Coax Cable Loss Calculator. Retrieved from https://www.zerdly.com/tools/coax-loss-calculator/
Tip: Enter any known values to calculate the remaining results.
Designed to run locally in your browser. Tool inputs are not intentionally stored by Zerdly unless stated otherwise.